A new method of fabricating transmission-blazed grating with period' s thickness of 10 nm or below by magnetron sputtering is proposed for the first time. The transmission-blazed grating model based on total reflection by inner interfaces is presented. Two examples of this grating used in water window are given, for example, angular dispersivie power 5.7 deg./nm; energy resolution λ/△λ≈104. LiF and LiBO2 etc. with high transmissivty are considered suitable for the grating' spacer material. Possible applications are discussed.